The present invention relates to an epoxy resin of excellent heat resistance, toughness and water proofness, an epoxy resin composition and a cured product thereof. The composition according to the present invention is extremely useful to a wide range of application uses such as molding materials, casting materials, laminate materials, composite materials, coating materials, adhesives and resists.
Epoxy resins are cured by various kinds of curing agents into cured products generally having excellent mechanical property, water proofness, chemical resistance, heat resistance and electric property and they have been utilized in a wide range of application uses such as adhesives, coating materials, laminates, molding materials and casting materials. An epoxy resin which has been industrially used most generally is a liquid or solid bisphenol A type epoxy resin obtained by reacting epichlorohydrine with bisphenol A. In addition, a flame retardant solid epoxy resin obtained by reacting tetrabromo bisphenol A with a liquid bisphenol A type epoxy resin or the like has been used industrially as a general-purpose epoxy resin.
Further, a polyfunctional epoxy resin prepared by entirely epoxidizing the alcoholic hydroxyl groups of the bisphenol A type epoxy resin has been reported in U.S. Pat. No. 4,623,701.
However, the general-purpose epoxy resin described above involves a drawback that the heat resistance is reduced although the toughness is increased in the cured product obtained by using this resin as the molecular weight thereof is increased. On the other hand, the cured product obtained from the polyfunctional epoxy resin obtained by entirely epoxidizing the alcoholic hydroxyl groups of the general-purpose epoxy resin has a drawback that it becomes brittle although the heat resistance is improved. Meanwhile, with remarkable development in the electronic industry or the like in recent years, heat resistance and toughness required for electric insulative materials used therefor has become severer and the development of an epoxy resin of excellent heat resistance and toughness has been demanded.